It's funny because I never hear that question. There are more objections to closing the vents than any other subject. I think the question that is really being asked is; is it worth it? My answer would be; how much is it worth to eliminate the crawl space from having problems? How much does it cost to remediate Mold, or treat for termites? Is it really worth replacing your roof before it leaks? You can see where I'm going with this. You are probably here on this blog because you are having problems or you know someone that is. Aside from fixing anything that is currently wrong it really is an investment in keeping it from getting worse and costing you more. The average cost of repairing rotted joist is about $3500, now that is not for replacing all of them but it does pay for around 10 or 15 to be replaced. We did a job in Linden Michigan in the Fall of 2008 that needed 22 joist and 45' of main beam replaced. It was a summer cabin the family used on the weekends and during Christmas time. The crawl space was 2200 sq ft and only 18" high, a bit of a challenge I might add. The homeowner (Tom) knew it needed to be fixed and was having trouble finding a company that wasn't trying to retire on his bank account. With this amount of damage it wasn't hard to see why the salesman's eyes would light up. In the end we installed a drain system and sump pump, closed seven foundation vents, our 16 Mil DrySpace and replaced the 22 rotted joists as well as the 45' of main beam. The price? Well, the structure repair was $8500 and the rest was another $8000. Hardly chump change for a weekend home, but Tom really didn't have any choice. It was that or ride it out until the floor fell in then walk away. I can tell you story after story about a homeowner that either inherited, bought or neglected a problem crawl space. Either way it still hurts.

Matt